Inazumi Underwater Cave Travel Guide

The Inazumi Underwater Cave, located in Bungoono, Oita Prefecture, is a natural wonder formed over millions of years. Created approximately 300 million years ago during the Paleozoic era, the cave took its present form when it was submerged following a major eruption of Mount Aso around 300,000 years ago. This geological event led to the creation of a unique underwater landscape, featuring countless stalactites, coral stones, and deep fissures.Visitors can explore the cave's illuminated pathways, discovering the Suichu Cave and Shinsei Cave sections, connected by artificial passages. The cave maintains a constant temperature of 16°C (61°F) year-round, providing a comfortable environment to view the geological formations. The clear streams are fed by the Hakusan River, known as one of Japan's 100 Exquisite and Well-Conserved Waters.The cave's history extends back to the Edo period, but it wasn't until 1976 that divers fully surveyed the system. Ongoing explorations continue to reveal new sections, with a 300-meter extension discovered in 2014, bringing the total surveyed length to approximately 1,000 meters.In addition to the cave itself, the surrounding area offers attractions such as the Showa Time Trip Romanza, a recreation of a 1950s-60s town, and a tall, gold-colored statue of the bodhisattva Kannon. For a unique experience, visitors can also enjoy a tent sauna near the cave entrance, cooling off in the cave's cold water afterward.